1. Field of the Invention
The present invention relates to an image reading apparatus and, more particularly, to an image reading apparatus configured to perform show-through reduction processing and foundation color reduction processing while reading an image from an original having images on both sides thereof.
2. Description of the Related Art
Conventionally, in image reading apparatuses such as scanners and facsimile machines, a background member which is read along with an original is provided in such a manner that it faces an image reading unit in order to form a background image formed with an image of the original. The color of the background member is typically chosen to be a white color similar to the foundation color of the original in order to maintain color fidelity of a white portion of the read image.
When both sides of a double-sided thin original are read using the white background member, printed information on the opposite side of the original can be seen through the original and a so-called show-through phenomenon is occurred. In order to solve the problem, a histogram is formed for each color component, a color to be removed from a read image is detected by using the histogram, and image processing is applied depending on the result of the detection. This can prevent show-through in a read image.
On the other hand, when an image of a original is read using a black background member, there is a problem that a margin area of the read image which has a color corresponding to the foundation color of the original is darkened because the contrast is reduced. To solve the problem, foundation color reduction processing is performed by using a histogram similar to those mentioned above to remove the color of the margin area (see for example Japanese Laid-Open Patent Publication (Kokai) No. 2005-192153).
However, the conventional image reading apparatus has a problem that the foundation color reduction processing cannot be performed until an image reading of at least one original is completed because it uses a histogram generated on the basis of an image read from the original to detect the foundation color. Another problem with the conventional image reading apparatus that uses histograms in show-through reduction processing and foundation color reduction processing is that the apparatus requires a memory for generating the histograms in addition to a memory for storing read images.